This invention relates to polymer dendrimers and more particularly to polymer dendrimers which impart both antioxidant and dispersant properties to a lubricant.
The basis for the present new development is in the preparation of polymer dendrimers which are known as "Starburst" dendrimers.
At Dow Chemical, Donald A. Tomalia has been developing families of compounds that he calls "starburst dendrimers". The word dendrimer derives from dendron, the Greek word for tree. At the University of South Florida, George R. Newkome has been developing other families of multibranched molecules that he has named "arborols"--from arbor, the Latin word for tree. Both chemists expect their new macromolecules to be useful for many purposes.
Explaining his work on starburst dendrimers, Tomalia notes that they have three distinguishing structural features; an initiator core, interior layers of repeating units radially attached to the core, and an outer surface of terminal functionality.
Dendrimer synthesis is a stepwise process. Any of several systems can be used to start and build up these "precision macromolecules". The polyamidoamines (PAMAMs) are probably furthest along in development. Their synthesis typifies the general approach.
In the first step of PAMAM synthesis, an initiator core such as ammonia or ethylenediamine (EDA) is reacted with methyl acrylate--the so-called Michael addition--to form a triester. In the second step, the triester is exhaustively amidated with a large excess of EDA to form a triamidoamine. Tomalia refers to this first-generation compound as a starbranch oligomer.
The stepwise procedure is repeated to form succeeding generations of starburst dendrimers, each with twice as many terminal groups as its predecessor. If ammonia is used as the initiator core, the progression is 3, 6, 12, and so on, up to 1536 for the 10th generation. With increasing size, the molecules tend to assume a spheroidal shape. In contrast, if EDA is used as the initiator core, the progression is 4, 8, 16, and so on. These molecules tend to become ellipsoidal.
Thus, in the present invention, it is an object to utilize this basic teaching of dendrimers to develop a useful anti-oxidant dispersant polymer dendrimer that imparts these properties to a lubricant.